In recent years, the modes of communication of phones have become diversified. In addition to conventional voice communication by line switching, phones capable of packet communication utilizing IP (Internet Protocol) networks are being widely utilized. For example, there is “chat mail” for conversations by mobile phones swapping e-mails in real time (see Patent Document 1). Chat mail is one of the modes of communication called “group communication” where pre-registered members form a group and swap text and other data in real time in this group.
In group communication, in general, one terminal in the group becomes a sender and the other terminals become receivers so that one-to-many communication is performed. In a case where a plurality of terminals participates in communication, it would be convenient if the terminal side can grasp what members are participating in communication at present. Accordingly, for example in the system disclosed in Patent Document 2, a management apparatus managing group communication provides a list of participating members to each terminal. This is displayed at a display unit of each terminal.
In such group communication, attempts are being made for voice communication utilizing VoIP (Voice over Internet Protocol). One of these is called “PoC (Push to talk over Cellular)”. In PoC, an SIP (Session Initiation Protocol) server manages the groups and the members in the groups and controls packetized voice calls (see Patent Document 3).
A terminal which starts group communication in PoC, for example as disclosed in Patent Document 3, sends a call request (confirmation notification of participation) to members in the group whom he wants to communicate with. When sending the call request, the management apparatus prepares a member list in the group database. The terminals of the members in the group, when receiving the call request, participate in group communication by answering that request.
When ending group communication in PoC, a request for end of communication is transmitted to the management apparatus managing the communication. The management apparatus, when receiving this end request, performs a predetermined procedure for ending the group communication and notifies the end of communication by completion of the procedure to the terminals in the group.
Patent Document 1: Japanese Patent Publication (A) No. 2005-18423
Patent Document 2: Japanese Patent Publication (A) No. 2005-136524
Patent Document 3: Japanese Patent Publication (A) No. 2005-518166